Wearing proved his point by doing a demonstration on a tub that a homeowner had run bleach through repeatedly to clean it. Using special cleaning agents that are heated and run through the circulation system for 20 minutes, it didn't take long for gunk to start coming out.

"Lumps of scale deposits, bath residue, soap scum, hair and the water actually changes color because of the dirt," Wearing explained.

And our demonstration was a home tub. Imagine a tub that lots of people have used like a hotel. You have no idea who the people are that used the tub before you or what they may have.

"Most of us go to a hotel and see inside of tub clean, but what we can't see is what can hurt us the bacteria that's harboring in those pipes," said Wearing.

Wearing said most hotels aren't interested in the professional cleaning service he sells because of price and the fact that guests don't complain. He said guests don't know to complain and if they do get sick, they might not associate it with the whirlpool tub because it sometimes takes 2 to 10 days for the symptoms to show.

The Centers for Disease Control reports it has investigated a number of outbreaks of Legionnaires' disease due to whirlpool baths.

"That is a very dangerous type of bacteria that you can actually catch by inhaling the bubbles," said Wearing.

So how do you know if a whirlpool bath you want to use has been professionally cleaned? You can look for a placard on display, or ask the hotel, gym, spa for proof of a cleaning. When it comes to your home, Wearing and the National Council for Whirlpool Bath Health and Safety recommend a professional cleaning once a year which will run you about $180.